Christopher Hyson MD, FRCPC, Clinical Fellow, Movement Disorders Program, London Health Sciences Centre, London, ON.

Mandar S Jog MD, FRCPC, Director, Movement Disorders Program, London Health Sciences Centre, London, ON.

Epidemiology
Idiopathic Parkinson's Disease (IPD), which results from degeneration of substantia nigra neurons, is characterized by the typical motor symptoms of rest tremor, rigidity, bradykinesia and postural instability. The estimated prevalence, which has been rising with the aging of the population, is 187/100,000 in the United States, with an annual incidence of 20/100,000. In addition to the well recognized motor disability, neuropsychiatric symptoms, such as depression, anxiety disorders and psychosis, are common, yet under-recognized in patients with IPD.¹ It is, therefore, important that primary care physicians, internists and neurologists who care for patients with IPD be familiar with the occurrence and management of this important symptom.

Depression is the most common neuropsychiatric symptom seen in patients with IPD. It is estimated that approximately 40% of patients with IPD will experience depression at some point over the course of their illness. For 4-6% of these patients, the episode will meet the Diagnostic and Statistical Manual of Mental Disorders' (DSM-IV) definition of major depression. The remainder will meet the diagnostic criteria for minor depression.